Does automotive glass protect you from the sun?

Justin Pritchard

Published: Feb 27 at 4:13 p.m.

Updated: Feb 28 at 5 a.m.

Don’t assume the glass in your vehicle offers any significant protection against the harmful rays of the sun.

Being the super-trendy guy that I am, I had a tattoo sleeve completed on my left arm last summer. Said arm spends no less than about 12 hours a week resting on the window ledge of a vehicle while I drive, often in the sun and often in a short-sleeved shirt.

Newly-tattooed skin is incredibly sensitive to the sun. You’re supposed to keep new tattoo work completely covered for a few weeks, as you’re not even supposed to apply sun-block until the skin is largely healed.

No problem: I purchased a white spandex sun-shielding sleeve that slips over my arm, lets my skin breathe and blocks the harmful rays from reaching my new tats.

I can wear this clever sleeve with a short-sleeve shirt, instead of wearing a long-sleeve shirt in the middle of summer, which is a bonus. This basically makes me a genius.

I went on a lengthy car ride not long after receiving that tattoo. Windows closed. AC blasting (it was a hot one). Arm on the window ledge. Peter Gabriel blasting on the stereo. This was a great day.

But I’d been inside all morning and started my drive without slipping on my cool-guy tattoo sleeve because it was cloudy.

The sun arrived an hour into my drive and, within about a minute, I felt an intense searing pain on my unprotected arm, looked down and saw a visible blister, right on my freshest tattoo. If bacon had a sense of touch, this is what it would feel while being crisply fried in a sizzling pan.

That’s delicious, but my arm probably isn’t. And at this moment the sun had, literally, cooked my now super-sensitive skin, right through the window of this car.

It was my own stupid fault for forgetting to protect myself, but it made me wonder: How much protection do the windows in your vehicle offer from the sun’s harmful rays?

Cancer under glass

Skin cancer can come about in various ways, but the main culprit, by a landslide, is the sun and, specifically, a form of UV radiation it constantly streams our way.

“The harmful UV rays that reach the earth from the sun are divided into UVB and UVA,” explains dermatologist Dr. Michelle Levy. “All of a car’s windows filter out the sun’s UVB rays, but not all windows will protect from all UVA rays.”

Dr. Levy says that the most significant risk relating to the formation of skin cancer is sun exposure.

“About 90 per cent of skin cancers are caused by the sun,” she says. “People who have fair skin and blue eyes and those who burn easily are at higher risk. Living in a warm, sunny climate will also increase one’s risk because of increased exposure.”

And do be careful if you have a sunroof and especially if you’re bald.

“There is data indicating that male pattern baldness is associated with a higher risk of skin cancer on the scalp,” adds Dr. Levy. “In my practice, I see far more sun damage and skin cancer involving the scalp in individuals who have lost their hair, than in men and women who haven’t.”

Case in point? My ultra-bald father, who is also our family’s sunblock police, recently had a skin cancer growth (successfully) removed from his scalp. Though dad never goes outside without plastering himself to completion with a thick layer of Coppertone; he has spent hours a week, for years, driving in his various vehicles beneath a (closed) glass sunroof panel. Here, dad never bothered to cover his lustrous noggin with sunblock and simply assumed that the sunroof glass was protecting him.

That probably wasn’t the case.

According to Dr. Levy, sun exposure through the sunroof glass was, in any likelihood, a leading factor in dad’s skin cancer growth.

“There are several different types of skin cancer,” Dr Levy adds. “The most common are basal cell carcinomas, followed by squamous cell carcinomas, sometimes collectively known as non-melanoma skin cancer. These types of skin cancers are much more common in areas that are frequently exposed to the sun, such as the face, scalp, chest, and the back of the hands.

“Melanoma is a more dangerous type of skin cancer, and most melanomas are more common in areas that are exposed to the sun less frequently, and may be more prone to intermittent sunburns. These include areas like the back, or the legs.”

Anyhow, don’t assume the glass in your vehicle offers any significant protection against the harmful (and possibly tattoo-sizzling, cancer-causing) rays of the sun. Some cars do. Others don’t. Some offer more protection, and others offer less.

Automakers pick the glass they’ll use in their vehicles for a wide range of reasons and UV protection may or may not be one of them.

Dr. Levy showed me a 2016 report indicating that front windshields blocked about 96 per cent of UV rays, although the coverage offered by other automotive glass tended to be lower, at about 71 per cent.

For instance, the sunroof glass used in a new Volvo XC90 blocks at least 99.5 per cent of UV radiation, according to that automaker.

“Automotive glass is designed to block most (and in some cases, all) of the sun’s UV rays,” said Brad Evans, Subaru Canada’s car line manager. “Laminated windshield glass typically blocks 100 per cent of UV rays, while side and rear window door glass blocks from 80 per cent up to 100 per cent. Sunroof glass with factory tinting is also very protective, blocking over 90 per cent of UV rays.”

But that’s just two automakers and your protection from UV rays at the wheel may vary.

Simply, motorists should understand that the windows in their vehicle likely block some UV rays, but that exposure, even in partially-filtered amounts is still dangerous when it comes to skin cancer.

“Even with a high degree of filtration of UV, some will still reach the skin,” Dr. Levy comments. “For these reasons, it is advisable that drivers protect themselves with sun-protective clothing and sunscreens. After-market UV films are also available, and may be advisable for those who spend a great deal of time in their cars.”

Based on this advice, Dad has recently installed a special 3M coating to the sunroof glass in his Tiguan, which blocks 100 per cent of the incoming UV rays.

And this isn’t just for long-haul drivers and truckers either. There’s no time limit that’s necessarily okay when it comes to sun exposure and skin cancer, especially on vulnerable individuals.

Dr. Elaine McWhirter, a medical oncologist, explains “sun safety with either sunscreen or SPF clothing really applies to anyone who spends a fair amount of time in their car — even commuters.”

Dr. McWhirter notes that left-arm cancer is more common in North America, where the driver’s left arm is exposed to the sun more often — either by hanging it out of the window, or resting it nearby.

In countries where drivers are positioned on the right-hand side of the vehicle, instances of skin cancer on the arm tend to be more right-arm heavy.

Remember — the side windows of your vehicle likely don’t offer as much protection from the sun as its windshield. And even that windshield may not block all harmful UV rays.

“The side windows, and presumably the sunroof glass, are made of tempered glass, which allows more UVA penetration,” Dr. Levy said. “This may be particularly relevant to the question of the bald driver and increased skin cancer risk. My experience as someone who treats with highly sun-sensitizing medications is that the car provides basically no protection — they still burn in minutes.”

Thankfully, protecting yourself is easy.

“The number one thing that people can do to reduce their risk of skin cancer is to protect their skin from the sun’s harmful rays,” Dr. Levy says. “This means using sun-protective clothing, hats, sunglasses and sunscreen and seeking shade whenever possible.”